Gyratory crushers are used for crushing ore, mineral and rock material to smaller sizes. The crusher includes a crushing head mounted upon an elongate main shaft. A first crushing shell (typically referred to as a mantle) is mounted on the crushing head and a second crushing shell (typically referred to as a concave) is mounted on a frame such that the first and second crushing shells define together a crushing chamber through which the material to be crushed is passed. A driving device positioned at a lower region of the main shaft is configured to rotate an eccentric assembly positioned about the shaft to cause the crushing head to perform a gyratory pendulum movement and crush the material introduced in the crushing chamber. Example gyratory crushers are described in WO 2004/110626; WO 2008/140375, WO 2010/123431, US 2009/0008489, GB 1570015, U.S. Pat. No. 6,536,693, JP 2004-136252, U.S. Pat. No. 1,791,584 and WO 2012/005651.
Gyratory crushers (encompassing cone crushers) are typically designed to maximise crushing efficiency that represents a compromise between crushing capacity (the throughput of material to be crushed) and crushing reduction (the breakdown of material to smaller sizes). This is particularly true for heavy-duty primary crushers designed for mining applications. The capacity and reduction may be adjusted by a variety of factors including in particular size of the crushing chamber, the eccentric mounting of the main shaft and the shape, configuration and setting of the opposed crushing shells.
For example, the design of the outer crushing shell has a significant effect on the capacity and reduction of the crusher. In particular, an outer crushing shell with an inner facing contact surface that tapers inwardly towards the mantle acts to accelerate the through-flow of material. However, conventional designs of this type fall short of optimising capacity whilst increasing reduction and there is therefore a need for an improved outer crushing shell with improved performance.